FIGS. 1 and 2 are assembled and exploded perspective views, respectively, of a conventional portable reading lamp 10. The portable reading lamp 10 includes a circuit board 20 on which plurality of light-emitting diode (LED) lights 21 are mounted. A positive electrode plate 22 and a negative electrode plate 23 are separately disposed at two ends of the circuit board 20 to connect to batteries. In addition, a switch mechanism 24 is arranged on the circuit board 20 for turning on/off the LED lights 21. A lower cover 30 and an upper cover 40 are assembled to each other to enclose the circuit board 20 therebetween. The lower cover 30 is located below the circuit board 20, and is formed at a bottom with a rectangular opening, via which the batteries can be moved into and out of the lower cover 30. A cover plate (not shown) having a shape corresponding to that of the rectangular opening is connected to the lower casing 30 for openably closing the rectangular opening. The lower cover 30 is further formed with a through hole, via which the switch mechanism 24 is partially exposed to an outer side of the lamp 10. In addition, a first long cut 31 is formed along an upper front edge of the lower cover 30 corresponding to a surface, from where the LEDs irradiate light. The upper cover 40 is assembled to a top of the lower casing 30, and is internally provided with locating members (not shown) for holding the circuit board 20, the positive and negative electrode plates 22, 23, and the switch mechanism 24 in place. A second long cut 41 is formed along a lower front edge of the upper cover 40. The first and the second long cut 31, 41 together define an elongated slot. The portable reading lamp 10 further includes a light-guiding plate 50 having a transparent plate 51 extended in a direction parallel to the lighting direction of the LED lights 20. The transparent plate 51 has a first edge inserted into the elongated slot defined by the long cuts 31, 41 to thereby assemble to the lower and upper covers 30, 40. A support strip 52 is mounted to a second edge of the transparent plate 51 opposite to the first edge in order to keep the transparent plate 51 in a horizontal state. Referring to FIG. 3, to use the portable reading lamp 10, first position the portable reading lamp 10 on a book or the like, and then switch on the LED lights 20 via the switch mechanism 24. At this point, light emitted from the LED lights 20 are projected into and transmitted along the light-guiding plate 50 to uniformly illuminate the book for reading.
The above conventional portable reading lamp 10 has the following disadvantages:
First, the light-guiding plate 50 is needed and must be extended in a direction parallel to the lighting direction of the LED lights 21, forming a limit in using the portable reading lamp 10;
Second, the light-guiding plate 50 is likely to reflect light projected thereto and causes discomfort to a user's eyes;
Third, the light-guiding plate 50 is subject to abrasion and scratches to form a scratched surface, which would cause degraded illumination quality to harm the user's vision; and
Fourth, with the existence of light-guiding plate 50, the portable reading lamp 10 is considerably large in size, making the lamp 10 inconvenient for carrying or storing.